Instrument Hook-up Drawing

Hook-up drawing is a detailed drawing showing typical installation of instrument in a correct manner so that instrument operates properly (gives accurate indication and prevent any issued which could potentially affect the measurement such as liquid trap in gas impulse line).
Hook-up drawing indicates tubing slopes, position of instrument in reference to process tapping point, scope break between instrument vs piping.
Hook-up drawing also gives information the requirement of bulk material for each installation. It also details its specification (size, type and material) and the quantity.

There are two types of hook-up drawing:

Process Hook-Up

This hook-up drawing contains typical installations for instrument which connects to the process

Pneumatic Hook-Up

This hook-up drawing contains typical installations for instrument which requires instrument air such as control valve, actuated valve

Reference drawing: P&ID, Installation Detail Specification, Piping Specification
P&ID tells the designer which instrument requires a hook-up drawing. A good designer can also read whether the instrument tapped in gas service or liquid service.
Battery limit between instrument and piping shall be made clear, this is stated in P&ID symbol and typical sheet or piping documents.
Installation detail specification will also specify items that should be utilized and factor that should be considered in one installation

The purpose of Instrument Hook Up Drawing

As stated earlier, information of the requirement of bulk material is stated for installation on each sheet hence the bulk material required for the whole drawings could be summarized and tabulated in a document named Material Take Off.

During project construction phase, this drawing is also referred as a guidance of how to install the instrument properly.